Sounds like we might be coming from different perspectives. I honestly don't use any DF libraries often, and really only Pandas. I used to use pandas a fair amount, but that was years ago, and now I only have to reach for it a few times a year. So maybe the docs are good for people that already have deeper experience. Because I think just the fact that you have used datafusion and duckdb illustrates that you're more skilled in this domain than I am, because I haven't used those haha.
But I do think making good docs is quite hard. You usually have multiple audiences that you might not even be aware of. Which makes one of the most important things to do is keep an open ear to listen for them. It's easy to get trapped thinking you got your audience but you're actually closing the door to many more groups (unintentionally). It's also just easy to be focused on the "real" work and not think about docs.
But I do think making good docs is quite hard. You usually have multiple audiences that you might not even be aware of. Which makes one of the most important things to do is keep an open ear to listen for them. It's easy to get trapped thinking you got your audience but you're actually closing the door to many more groups (unintentionally). It's also just easy to be focused on the "real" work and not think about docs.